package com.jcnet.bizaia.tools;
import java.io.UnsupportedEncodingException;

/**
 * Project : DESTest
 * Package : 
 * File    : Hex.java
 */

/**
 * <code>Hex</code>
 * description.<p>
 * 
 * <blockquote><pre>
 * use for ...
 * </pre></blockquote>
 * 
 * @author Zhou Yin (<a href="mailto:vambad@gmail.com">Contact Me</a>)
 * @version 1.0, 2013-10-30
 * @since 1.0
 */
public class Hex {

	/**
	 * Default charset name is {@link CharEncoding#UTF_8}
	 */
	public static final String	DEFAULT_CHARSET_NAME	= "UTF-8";

	/**
	 * Used to build output as Hex
	 */
	private static final char[]	DIGITS_LOWER			= { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };

	/**
	 * Used to build output as Hex
	 */
	private static final char[]	DIGITS_UPPER			= { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F' };

	/**
	 * Converts an array of characters representing hexadecimal values into an array of bytes of those same values. The
	 * returned array will be half the length of the passed array, as it takes two characters to represent any given
	 * byte. An exception is thrown if the passed char array has an odd number of elements.
	 * 
	 * @param data
	 *            An array of characters containing hexadecimal digits
	 * @return A byte array containing binary data decoded from the supplied char array.
	 * @throws DecoderException
	 *             Thrown if an odd number or illegal of characters is supplied
	 */
	public static byte[] decodeHex(char[] data) throws Exception {

		int len = data.length;

		if (( len & 0x01 ) != 0) {
			throw new Exception( "Odd number of characters." );
		}

		byte[] out = new byte[len >> 1];

		// two characters form the hex value.
		for (int i = 0, j = 0; j < len; i++) {
			int f = toDigit( data[j], j ) << 4;
			j++;
			f = f | toDigit( data[j], j );
			j++;
			out[i] = (byte) ( f & 0xFF );
		}

		return out;
	}

	/**
	 * Converts an array of bytes into an array of characters representing the hexadecimal values of each byte in order.
	 * The returned array will be double the length of the passed array, as it takes two characters to represent any
	 * given byte.
	 * 
	 * @param data
	 *            a byte[] to convert to Hex characters
	 * @return A char[] containing hexadecimal characters
	 */
	public static char[] encodeHex(byte[] data) {
		return encodeHex( data, true );
	}

	/**
	 * Converts an array of bytes into an array of characters representing the hexadecimal values of each byte in order.
	 * The returned array will be double the length of the passed array, as it takes two characters to represent any
	 * given byte.
	 * 
	 * @param data
	 *            a byte[] to convert to Hex characters
	 * @param toLowerCase
	 *            <code>true</code> converts to lowercase, <code>false</code> to uppercase
	 * @return A char[] containing hexadecimal characters
	 * @since 1.4
	 */
	public static char[] encodeHex(byte[] data, boolean toLowerCase) {
		return encodeHex( data, toLowerCase ? DIGITS_LOWER : DIGITS_UPPER );
	}

	/**
	 * Converts an array of bytes into an array of characters representing the hexadecimal values of each byte in order.
	 * The returned array will be double the length of the passed array, as it takes two characters to represent any
	 * given byte.
	 * 
	 * @param data
	 *            a byte[] to convert to Hex characters
	 * @param toDigits
	 *            the output alphabet
	 * @return A char[] containing hexadecimal characters
	 * @since 1.4
	 */
	protected static char[] encodeHex(byte[] data, char[] toDigits) {
		int l = data.length;
		char[] out = new char[l << 1];
		// two characters form the hex value.
		for (int i = 0, j = 0; i < l; i++) {
			out[j++] = toDigits[( 0xF0 & data[i] ) >>> 4];
			out[j++] = toDigits[0x0F & data[i]];
		}
		return out;
	}

	/**
	 * Converts an array of bytes into a String representing the hexadecimal values of each byte in order. The returned
	 * String will be double the length of the passed array, as it takes two characters to represent any given byte.
	 * 
	 * @param data
	 *            a byte[] to convert to Hex characters
	 * @return A String containing hexadecimal characters
	 * @since 1.4
	 */
	public static String encodeHexString(byte[] data) {
		return new String( encodeHex( data ) );
	}

	/**
	 * Converts a hexadecimal character to an integer.
	 * 
	 * @param ch
	 *            A character to convert to an integer digit
	 * @param index
	 *            The index of the character in the source
	 * @return An integer
	 * @throws DecoderException
	 *             Thrown if ch is an illegal hex character
	 */
	protected static int toDigit(char ch, int index) throws Exception {
		int digit = Character.digit( ch, 16 );
		if (digit == -1) {
			throw new Exception( "Illegal hexadecimal charcter " + ch + " at index " + index );
		}
		return digit;
	}

	private final String	charsetName;

	/**
	 * Creates a new codec with the default charset name {@link #DEFAULT_CHARSET_NAME}
	 */
	public Hex() {
		// use default encoding
		this.charsetName = DEFAULT_CHARSET_NAME;
	}

	/**
	 * Creates a new codec with the given charset name.
	 * 
	 * @param csName
	 *            the charset name.
	 * @since 1.4
	 */
	public Hex(String csName) {
		this.charsetName = csName;
	}

	/**
	 * Converts an array of character bytes representing hexadecimal values into an array of bytes of those same values.
	 * The returned array will be half the length of the passed array, as it takes two characters to represent any given
	 * byte. An exception is thrown if the passed char array has an odd number of elements.
	 * 
	 * @param array
	 *            An array of character bytes containing hexadecimal digits
	 * @return A byte array containing binary data decoded from the supplied byte array (representing characters).
	 * @throws DecoderException
	 *             Thrown if an odd number of characters is supplied to this function
	 * @see #decodeHex(char[])
	 */
	public byte[] decode(byte[] array) throws Exception {
		try {
			return decodeHex( new String( array, getCharsetName() ).toCharArray() );
		} catch (UnsupportedEncodingException e) {
			throw new Exception( e.getMessage(), e );
		}
	}

	/**
	 * Converts a String or an array of character bytes representing hexadecimal values into an array of bytes of those
	 * same values. The returned array will be half the length of the passed String or array, as it takes two characters
	 * to represent any given byte. An exception is thrown if the passed char array has an odd number of elements.
	 * 
	 * @param object
	 *            A String or, an array of character bytes containing hexadecimal digits
	 * @return A byte array containing binary data decoded from the supplied byte array (representing characters).
	 * @throws DecoderException
	 *             Thrown if an odd number of characters is supplied to this function or the object is not a String or
	 *             char[]
	 * @see #decodeHex(char[])
	 */
	public Object decode(Object object) throws Exception {
		try {
			char[] charArray = object instanceof String ? ( (String) object ).toCharArray() : (char[]) object;
			return decodeHex( charArray );
		} catch (ClassCastException e) {
			throw new Exception( e.getMessage(), e );
		}
	}

	/**
	 * Converts an array of bytes into an array of bytes for the characters representing the hexadecimal values of each
	 * byte in order. The returned array will be double the length of the passed array, as it takes two characters to
	 * represent any given byte.
	 * <p>
	 * The conversion from hexadecimal characters to the returned bytes is performed with the charset named by
	 * {@link #getCharsetName()}.
	 * </p>
	 * 
	 * @param array
	 *            a byte[] to convert to Hex characters
	 * @return A byte[] containing the bytes of the hexadecimal characters
	 * @throws IllegalStateException
	 *             if the charsetName is invalid. This API throws {@link IllegalStateException} instead of
	 *             {@link UnsupportedEncodingException} for backward compatibility.
	 * @see #encodeHex(byte[])
	 */
	public byte[] encode(byte[] array) throws Exception {
		String string = encodeHexString( array );
		if (string == null) {
			return null;
		}
		try {
			return string.getBytes( charsetName );
		} catch (UnsupportedEncodingException e) {
			throw new Exception( charsetName, e );
		}
	}

	/**
	 * Converts a String or an array of bytes into an array of characters representing the hexadecimal values of each
	 * byte in order. The returned array will be double the length of the passed String or array, as it takes two
	 * characters to represent any given byte.
	 * <p>
	 * The conversion from hexadecimal characters to bytes to be encoded to performed with the charset named by
	 * {@link #getCharsetName()}.
	 * </p>
	 * 
	 * @param object
	 *            a String, or byte[] to convert to Hex characters
	 * @return A char[] containing hexadecimal characters
	 * @throws EncoderException
	 *             Thrown if the given object is not a String or byte[]
	 * @see #encodeHex(byte[])
	 */
	public Object encode(Object object) throws Exception {
		try {
			byte[] byteArray = object instanceof String ? ( (String) object ).getBytes( getCharsetName() ) : (byte[]) object;
			return encodeHex( byteArray );
		} catch (ClassCastException e) {
			throw new Exception( e.getMessage(), e );
		} catch (UnsupportedEncodingException e) {
			throw new Exception( e.getMessage(), e );
		}
	}

	/**
	 * Gets the charset name.
	 * 
	 * @return the charset name.
	 * @since 1.4
	 */
	public String getCharsetName() {
		return this.charsetName;
	}

	/**
	 * Returns a string representation of the object, which includes the charset name.
	 * 
	 * @return a string representation of the object.
	 */
	public String toString() {
		return super.toString() + "[charsetName=" + this.charsetName + "]";
	}

}
